1)to say in a celebratory fashion that something is on point, or precise.
2)to acknowledge an accomplishment-small or large.
3) sometimes it describes a noun, rather than using the noun's name.
Example: that winning 3 point shot was on that ass!
Example: Egdar: I just came up 400 dollars at that craps table.
Rey: On that ass!
Example: instead of saying" I came up 300 dollars at the Flamingo", you would say "I came up 300 dollars on that ass"